Electrosurgical units (ESU) are routinely used in operating rooms and are known to interfere with the monitoring of patients' bio-potential signals (e.g. electrocardiogram signals, electroencephalography signals, blood pressure, etc.). An ESU applies a large amplitude (e.g., 100 V-5 kV) and high frequency (>300 kHz) signal to a patient's body for operations. However, the ESU signal may also have energy at lower frequencies (e.g., from direct current to 100 Hz) because the high-frequency ESU signal amplitude is modulated due to cutting and subsequently rectified when a current passes through ESU electrodes. As a result, the lower frequency components of the ESU signal may generate noises in the pass band of bio-potential signals of interest. Such noise often produces false alarms (e.g., a high heart rate) in software algorithms that monitor the bio-potential signals.